Technical Field
The invention relates to a method of homogenizing a liquid, in particular a colorant for paint, in a container. The invention further relates to an assembly for dispensing a liquid comprising a container and a pump and to an apparatus comprising a plurality of such assemblies.
Background of the Related Art
Brownian motion of particles suspended in liquids is not sufficient to overcome gravitational forces and such particles tend to settle out of the liquid and agglomerate. The paint industry has struggled with this problem for more than a hundred years. It is still widely believed within this industry that in order for a pigmented colorant to be successfully applied using colorant dispensers the dispersion must be stirred. This requirement places stringent demands on the manufacturers of dispensers, especially when colorants contain a high loading of pigment.
EP 2 198 950 relates to an apparatus (denoted by numeral 1 in the Figures of that publication) for dispensing a plurality of fluids, comprising a support, such as a turntable (2) or a linear table, a plurality of containers (4) for holding a fluid mounted on the support (2), pumps (3) connected to respective containers (4), a common actuator (31) for sequentially operating the pumps (3), stirring elements mounted rotatably inside and extending from the containers (4), and a drive mechanism (21) for rotating the stirring elements, wherein the support (2) on the one hand and the actuator (31) and drive mechanism (21) on the other are movable relative to each other. The drive mechanism (21) comprises a protrusion (26) movable between at least a first, extended position (FIG. 2B) for engaging a stirring element (20) and a second, retracted position (FIG. 2A).
WO 2008/110606 relates to a canister assembly comprising an annular outer shell (21) with an outer cylindrical wall connected to a bottom which, in turn, is connected to an inner cylindrical wall that serves as a standpipe. The bottom includes an outlet (29) connected to a pump. A hollow agitator shaft (21) slides over the inner standpipe and includes a plurality of outwardly extending blades (32) for stirring or “agitating” the fluid.
EP 1 908 510 relates to a device for mixing fluids, particularly paints and varnishes. The Figures of this publication shows a storage tank (2) containing a stirring element. GB 1,004,721 also discloses stirring devices.
In practice, stirrers get contaminated, the colorants will dry in, and over time a buildup of thin layers of colorant will form on the stirrers. The dried layers can be a serious cause of contamination when pieces of the layers break away and drop in the colorant. This might even cause blocking of a downstream pump or contamination of the paint.
Another disadvantage is that stirrers inevitably cause a lot of interaction between the colorant and the atmosphere above the colorant, resulting in evaporation of solvent and in oxidation.
It is an object of the present invention to provide a method of homogenizing a liquid, in particular a colorant for paint, in a container, that does not require a stirrer.